North Atlantic Climate Studies
Tom Rossby and Lew Rothstein are
co-principal investigators of a combined observational and numerical
investigation of the North Atlantic Current system in the Newfoundland
Basin region of the North Atlantic. The observational program
involves the release of approximately 100 Lagrangian subsurface
drifters, which return via satellite time series of temperature,
pressure, location, and local stretching vorticity after a mission of
(typically) ten months.
The modeling component of the program is divided into at least
three distinct efforts:
- a process study of intergyre exchange
using a simple version of the University of Miami Miami
Isopycnal Coordinate Ocean Model or MICOM
(Dutkiewicz, Rothstein),
- a process study of western boundary
current separation in the presence of a meridional overturning cell
using an even simpler layered quasigeostrophic model developed here
(Rowley, Rothstein), and
- a regional simulation of the
Newfoundland Basin using the Princeton University Princeton Ocean
Model or POM
configured for a limited domain, with realistic climatology and
surface forcing (Rowley, Rothstein).
As the Gulf Stream forms the North Atlantic Current offshore of the
southern "tail" of the Grand Banks, apparently in a very energetic eddy
field, part of its transport is returned as a recirculation, part makes
it around the tail of the Banks to form the North Atlantic Current, and
another part is the source for the water supplied to the Azores
Current. Also present in the Newfoundland Basin region (the deep water
off the Grand Banks, east to the Mid-Atlantic Ridge) is the Deep
Western Boundary Current, flowing south along the continental slope.
This deep flow is returning some of the North Atlantic Current
transport of warm, salty surface water to the north, as cold, dense
water flowing south, supplying deep water through the North and South
Atlantic and into the Indian, Pacific, and Antarctic Oceans. The role
of the meridional thermohaline circulation reflected in the DWBC on the
North Atlantic Current separation behavior and the formation of the
Azores Current from the Gulf Stream/North Atlantic Current is the
current focus of my research.
My primary modeling tool for this project is an N-layer
quasigeostrophic model that can be run efficiently with irregular
geometry. A document describing the model is available in both
dvi and
postscript
form.
In order to take advantage and extend the analysis of a new regional
climatology under development here at GSO by Ed Kearns, a student in the
Rossby group, I have configured the
Princeton Ocean
Model (POM) as a regional model for studying the behavior of the
North Atlantic Current in the Newfoundland Basin. Preliminary
diagnostic runs with the Kearns climatology are encouraging, and we
hope to have a full prognostic run completed soon.
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